2013 Bentley Continental GT V-8

Bentley Builds a Fuel Sipper We're Excited About

At the 2008 Geneva autoshow, Bentley's then-CEO Dr. Franz-Josef Paefgen announced, "A new powertrain will be introduced by 2012, delivering a 40-percent reduction in fuel consumption, while maintaining current levels of performance." His engineers shuddered.In December 2011, when we drove a late prototype of the new car, chief engineer Brian Gush told us a story from back in early 2008. Turns out that Gush's team, together with Audi engineers, were already working on a new V-8. Herr Paefgen asked them what they thought it would be capable of. They mentioned a best-case scenario of a 40% improvement in fuel efficiency, but they didn't quite know how they'd do it -- or if they could do it at all. Regardless, Paefgen promptly wrote "40-percent" into his speech and that was that. Missing the good doctor's target was no longer an option.

Fast forward to the 2012 Detroit Auto Show and Bentley's new CEO Wolfgang Durheimer just introduced that power train. It's comprised of a 500 hp, 4.0-liter twin-turbo V-8 that's capable of producing 487 pound-feet of torque mated to an eight-speed automatic transmission, available in both the coupe and convertible Continentals. Bentley claims that the extra gears, fewer pistons, smaller displacement and modern technologies like direct injection and cylinder deactivation help reduce thirst by 40%, though the EPA numbers have yet to be released.However, we've already driven a prototype and it seems to meet Paefgen's billing. The 2012 Continental GT V-8 feels as if it matches the performance of the previous-generation twin-turbo, 6.0-liter W-12-engined Continental GT. Bentley claims on the European test cycle the new engine and transmission team up to produce 40 percent better mileage, and that the car emits 40 percent less CO2. We can't wait to verify at least the first part of the claim. The only bitter note is that it's an extremely complicated, expensive engine, and when spec'd to the max, the V-8 can approach the cost of the W-12.

Complicated? You might remember some of this engine's highlights from the recent Audi S8 introduction, though the Bentley, with different inlet and exhaust paths and a different brand position, makes slightly less power, but more torque lower down in the rev range, and a rather more enchantingly bellicose noise.

Fuel is injected directly, to allow for higher compression and hence more power per liter. A pair of low-inertia, twin-scroll turbochargers are mounted in the V, and to keep the plumbing lengths short and response times sharp, the exhaust manifolds also exit into the V rather than outboard of the banks. There's a water-to-air intercooler tucked up there in the V too, with the water circuit's coolers down in the nose. This is heavier and more complex than simply taking the induction air down to the nose and back, but because the air path is shorter, response is, again, better. It almost goes without saying that there's variable valve timing on all four camshafts.

These measures make the new Bentley powerful, torquey, urgent and efficient. They're responsible for more than a third of the necessary fuel savings. Another slice comes from using a modified ZF eight-speed transmission, instead of the six-speeder in the W-12. It is of course capable of finding the most efficient ratio for the occasion, but it also slips into neutral at a standstill when the driver has a foot on the brake, saving engine drag.Other fuel-saving measures include new power steering, low-resistance tires, better aero drag, and so on. But the other headline item is another engine tweak, the variable displacement. Electromagnetic actuators can slide selected cam lobes along the shafts, leaving valves shut. The engine runs as a V-4 with the remaining four cylinders idle, flowing no air and using no gas.

The deactivation can occur at light load from 1500 to about 3000 rpm, which means it will stay as a V-4 up to 80 mph even on a slight uphill; engineers say it saves almost 10 percent in real-world driving. Which is useful, but to ensure the engine is fittingly smooth and quiet for a Bentley, it uses active engine mounts and active exhaust paths to reconfigure itself for four-cylinder operation. Sure enough, in use, we could never detect any kind of transition. Of course no one cares how this 200 mph sled feels at light throttle. You want to know about the blood and guts of the thing when you floor it. Good news!

Its torque figure, 487 lb-ft, is just six percent shy of the current W-12's in the 2012 Continental GT. It arrives at 1700 rpm and stays that way until 5000. Maximum power of 500 hp is achieved at 6000 rpm, just shy of the 6250 rpm redline. As soon the V-8's in it's wide torque band, you get a deep rumble that hardens intoxicatingly to something close to a bark at the higher register of the tachometer. Turbo lag just doesn't show its face, and the transmission responds promptly whether it's the ECU or your paddle-shifts that determine the timing. Shifts are smooth and the torque converter is almost always locked, for a sense of direct connection. Lifting the throttle leaves no messy over-running. This is a motor that simply does your bidding.The handling is more agile and responsive, too. Bentley claims it's thanks to a 55-pound weight loss up front. But that's ridiculous, considering the V-8 is still a 5000 pound+ machine. We think the improvements come from small suspension tweaks that make the big boy more resistant to understeer, more neutral and more tossable. Adaptive dampers and air springs give a remarkably pliant road ride while keeping body heave and roll in check.This might have been a prototype, but it felt very finished. It's too early to call Bentley's V-8 gamble a success, but we're sharpening our elbows to cut to the front of the line for the finished vehicle later this Spring.